Silver-resin print paper



United States Patent Ofi 3,157,510 Patented Nov. 17,1964

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3,157,510 SEVER-RESIN PRINT PAPER Charies F. Amering and Edward C.Yaclrel, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Filed Apr. 2, 1962, Ser. No. 184,562 7tllaims. (Cl. 96-114) This invention relates to photography andparticularl to a method and material for preparing stable silverphotographic images.

It is well known to prepare silver photographic images by exposure andprocessing of developing-out materials in which the photosensitive agentis silver halide, dispersed in gelatin coated on a suitable support likepaper, transparent film, glass or metal. When such materials are used,the silver image is produced in the gelatin layer.

Gelatin is an excellent dispersant and vehicle for preparing silverhalide emulsions and being water permeable facilitates processing withaqueous solutions.

Unfortunately, gelatin also has several shortcomings. It is hygroscopic,subject to attack by microorganisms, mites, cockroaches, etc. It changesin flexibility With temperature, humidity, and aging. It is ditiicult tocompletely remove emulsion addenda, residual silver salts, andprocessing chemicals from gelatin coatings. These in time, especially athigh relative humidity and temperature, may decompose and causebackground stain, image toning or fading, and mottle.

One object of the invention is to provide a photographic material, whichhas the benefit of the presence of gelatin during the preparation andcoating of the emulsion and the development of the silver image, and theadvantage of the absence of gelatin in the finished photograph.

Another object of the invention is to provide a photographic elementfrom which a silver halide photographic print may be obtained havingphysical characteristics which do not change with temperature orhumidity.

A further object of the invention is to obtain photographic prints whichare pliable, resistant to abrasion and cracking, and to attack bymicroorganisms, mites, cockroaches, etc. Other objects of the inventionwill appear herein.

These objects are achieved by the use of a photographic s lver halideelement in which the matrix or carrier for the silver salt consistssubstantially of a dispersion of about 60 to 95 percent by weight ofminute particles of a water-insoluble soft acrylate polymer resin in acontinuum of about to 40 percent by weight of unhardened gelatin.

After the photographic element has been exposed and processed in aconventional manner, it may conveniently be washed in warm water at 90to 150 F. This treatment dissolves and removes the gelatin and enablesthe resin particles to coalesce in a thin continuous layer which adheresstrongly to the support and entraps and retains the image silver. Theresin layer is flexible, resistant to cracking and abrasion, andpresents a surface sufiiciently smooth and glossy to obviateferrotyping.

The gelatin used in the preparation of our photosensitive layers, bothfor precipitating the silver halide and as the film-forming binder, isof low jelly strength, preferably below 100 grams Shoom, the optimumvalue being about 50 grams Shoom. Glues such as fish glue and gums suchas gum arabic, may be employed instead of or in addition to the gelatin.Gelatins used in the preparation of conventional photographic emulsionshave a Shoom value above 200 grams.

The Water-insoluble acrylate resins useful in this invention comprseacrylate polymers, for example homopolymers of methyl acrylate, ethylacrylate, isopropyl acryalte,

n-propyl acrylate, n-bntyl acrylate and isobutyl acrylate and theircopolymers with acrylonitrile. The level of aorylonitrile units in theresin should be not more than about percent of the total weight of themonomer units. The acrylate polymers are used in the form of latices orresin hydrosols having not more than about 50 percent solids content(resin hydrosols containing higher proportions of solids are less stableand tend to precipitate some of the resin). Resins of the preferred typeare soft, that is, the resin particles tend to coalesce to form acontinuous film when coated on a support and dried. The presence ofgelatin and the surfactant used in forming the hydrosol prevents theresin from coalescing when the photographic emulsions coatings are driedin manufacture.

The physical characteristics of the finished product can be variedconsiderably by selection of the resin for use in the photographicelements of our invention. If a slightly adhesive surface is wanted forexample to facilitate mounting a positive transparency on a glass slide,a soft resin with a relatively high ratio of alkyl acrylate toacrylonitrile can be used. If an abrasion-resistant final product isdesirable, the use of a higher ratio of acrylonitrile results in aharder print.

Resin to gelatin ratios (dry weight) useful in this invention range from:40 to 95:5 (resin to gelatin) with the preferred range from resin:30%gelatin to 99% resin: 10% gelatin. When a layer representing thiscombination is washed after processing in warm to hot water (attemperatures between about to F. for about 30 seconds or longerdepending on the temperature of the wash water, pressure applied,compositions used, etc.), the gelatin is eliminated thus leaving thecoalesced resin film containing the developed silver image on thesupport.

Developing agents can be incorporated in the photographic emulsion ifdesired but they must be selected from compounds that do not tangelatin, under the processing conditions to be used. 7

The emulsion can be coated on a variety of supports, for example, glass,transparent film like cellulose ester, polyolefins, polyester, etc.,fiber glass, translucentized paper, baryta-coated paper, waterproofpaper, etc. The support should be free of hardening agent which mightotherwise wander into the emulsions and harden the gelatin.

The ratio of silver to the gelatin-resin vehicle is not critical but wefind that a proportion of about one mole of silver halide to about 250to 400 grams of the gelatin-resin is preferable, as lower ratios tend toretard processing and higher ratios tend to give images of poor quality.

The most useful pH range for our silver halide, gelatin, resin hydrosolcompositions when coat ng onto a support is from about 5.0 to 7.0.

During processing of the'latent image, after exposure, the exposedsilver halide is converted to metallic silver and the residual silverhalide is removed by conventional nonhardening fixing techniques. Theprocessed material is washed in warm to hot water of about 90 to 150 F.to remove the gelatin.

The following examples illustrate but do not limit our invention.

Example 1 To a liquefied and stirred silver halide gelatin emulsion at40 C. containing one mole of a silver bromoiodide (80 mol percent of thehalide being bromide) and 20 grams of gelatin with a jelly strength of50 grams Shoom, were added 300 grams of 50% aqueous dispersion of awater-insoluble soft resin which resin comprises essentially a copolymerof 75% methylacrylate and 25% acylonitrile units by Weight. To this wereadded 400 grams of water and 500 grams of a 20% aqueous solution of alow-grade gelatin having a value of 50 grams Shoom. (The gelatin usedwas soluble in water at room temperature.) This mixture was coated on112 pound paper stock to give 0.4 gram of solids per square foot anddried.

A sample of the above coating was exposed through a' photographicnegative and processed in Kodak Developer D72, diluted 1:1, for twominutes, bathed in 1 percent 1 acetic acid stop bath for 15 seconds,fixed in Kodak fixing bath F-24 for 4 minutes, washed in water at 100 F.for 2 minutes, and dried. a

The dried photographic prints were noncurling, had

excellent flexibility, and were resistant to abrasion. The

Example 2; I

The emulsion of Example 1; was used with the exception that the softresin dispersion consisted of solids made from 90% ethylacrylate andacrylonitrile. The emulsion was coated on'a subbed film support ofcellulose acetate. The emulsion coating was exposed through aphotographic negative and processed to a positive by the The positivewas fixed in Kodak fixing bath F-24 for four minutes, and transferred toa water wash. All steps were carried out at room temperature of 70.

The positive while still wet was washed for 2 minutes in wash water at100 F. and was then squeezed into contact with a glass plate as alantern slide. The processed and mounted lantern slide showed reducedfading in the highlight areas when compared to a similarly processedcontrol which was also mounted on glass. The print made from the resincontaining emulsion prior to being mounted on glass was tacky and ifleft unmounted would have abraded easily or would have retained anyfingerprints, dirt, or lint which came into contact with it because ofthis tackiness.

I Example 3' I To a liquefied and stirred silver halide gelatin emulsionat 40 'C. containing one mole of silver chloride and 2-0 grams of aphotographic grade of gelatin having a Shoonr value of 43 grains, wereadded 280 grams of an aqueous dispersion of polymethylacrylate (47%solids). To. this was added a solution containing 500 cc. of water and300 grams of a 20% solution of a photographic gelatinhaving ,a Shoomvalue of' 43 grams. This mixture was coated to give 0.5 gram of solids,per square foot and dried.

This coating was exposed and processed as in Example 1. The dried printwas noncurling, flexible, resistant to Y abrasion and had a surfacegloss equivalent to a ferro typed print. a This print was subjected toexposure on a shelf in an open-sided, roofed enclosure inPanamajtropicalconditions) for three months along with a conventionalphotographic paper print prepared by conventional procedures. Theresults indicated that the acrylate-resin containing print did not turnbrown, the highlights remained at full density and the print did notpitfrom the tone,reduced highlights and surface pitting from fungusgrowthi 7 growth of fungi. The control print exhibited a warmer 4Example 4 The coating was exposed to a line negative and processed inKodak Developer D ll for 2 minutes, rinsed in Kodak stop bath SB-la for10 seconds and fixed in Kodak fixing bath 1 -24 for 4 minutes. The lineprint was then washed in warm water at 120 F. for 2 minutes and dried.The print was noncurling, and was resistant to abrasion. The print wassubjected to exposure on a shelf in Panama for 3 months as in Example 3.N0 stain or reduction in highlight density was noted. This was comparedto the same control coating used in Example'3. This experiental coatingdid not pit from the growth of fungi.

Example 5 V The emulsion in Example 3 was used except the solids in theresin dispersion used as par-t of the colloid consisted of 60%isopropyl-acrylate and 40% acrylom'trile. The coating was processed asin Example 1. The dried print was noncurling, had excellent flexibilityand was very resistant to abrasion. The surface gloss was at least equalto a ferrotyped print. I

Aprint made from this coating. was subjected to exposure for 3 months inPanama as in Example .3. No stain nor reduction in highlight densityvwas noted. The amount of fungi that was on the surface was about equalto the experimental coatings in Examples 3 and 4 and again showed nosurface pitting from the growth of fungi. I V

The advantages of our material over prior art materials are nowapparent. The products of our invention reducethe problems dueto'fingerprints, smudges, accition. They are :also free from attack bymicroogranisms, mites, etc. I

The photographic emulsions used in practicing our invention are of thedeveloping-out type. They can be chemically sensitized by any of thewell-known chemical sensitizers by any of the accepted procedures. The.

emulsions may also be optically sensitized providing the sensitizingdyes do not react with or dissolve in the polymer to give colors orstain. The emulsions can containv stabilizing agents if desired.

We claim:

1. 'A photographic element from which photographic prints resistant totropical conditions may be prepared which comprises a support bearing alayer comprising photosensitive silver halide and a vehicle thereforcom-I posed of about 60-95% by weight of a water-insoluble resinselected from the group consisting of the homopolymers of alkylacrylates, the 'alkyl being 1-4carbon atoms and their copolymers withac'rylonitrile in which the level of the acrylonitrile units is no morethan about 50% of the total'weight of the monomer units dispersed inunhardened, low jelly strength gelatin of less than grams Shoom jellystrength. I

2. A photographic element'from which photographic prints resitant totropical conditions may be prepared which comprises a support bearing alayer of photosensitive silver halide and ,a vehicle therefor composedof about 60-95% by weight 'of a water-insoluble resinof 50-100% alkylacrylate, which resin is dispersed in unhardened, low jelly strengthgelatin of less than 100 grams Shoom jelly strength.

3. A photographic element from which photographic prints resistant totropical conditions may be prepared which comprises a support bearing alayer of photosensitive silver halide and a vehicle therefor Composed ofabout 6095% by weight of a methyl acrylate-acrylonitrile resin, theacrylate comprising at least 50% thereof which resin is dispersed inunhardened, low jelly strength gelatin of less than 100 grams Shoomjelly strength.

4. A photographic element from which photographic prints resistant totropical conditions may be prepared which comprises a support bearing alayer of a photosensitive silver halide and a vehicle therefor composedof about 60-95% by weight of polymethyl acrylate resin dispersed inunhardened, low jelly strength gelatin of less than 100 grams Shoomjelly strength.

5. A photographic element from which photographic prints resistant totropical conditions may be prepared which comprises a paper supportbearing a layer of photosensitive silver halide and a vehicle thereforcomposed of approximately 88% by Weight of a water-insoluble methylacrylate-acrylonitrile resin, the acrylate '-\comprising about 75%thereof which resin is dispersed in unhardened, low jelly strengthgelatin of less than 100 grams Shoom jelly strength.

6. The process of preparing a gelatin-free photographic silver image ina water-resistant resin layer on a support comprising the steps ofsubjecting a photographic element comprising a support and a layer ofphotosensitive silver halide in a vehicle of 60-95% by weight of awater-insoluble resin selected from the group consisting of thehomopolymers of alkyl acrylates, the

alkyl being 1-4 carbon atoms and their copolyrnerswith acrylonitrile inwhich the level of the acrylonitrile units is no more than about 50% ofthe total weight of the monomer units dispersed in unhardened, low jellystrength gelatin to the steps of (1) exposing, (2) developing, (3)fixing, and (4) washing in warm Water thereby removing substantially allof the gelatin from the layer.

7. A photographic element from which photographic prints resist-ant totropical conditions may be prepared which comprises a support bearing alayer comprising photosensitive silver halide and a vehicle thereforcomposed of about 60-95% by weight of a water-insoluble resin selectedfrom the group consisting of the homopolymers of alkyyl acrylates, thealkyl being l-4 carbon atoms and their copolymers with acrylonitrile inwhich the level of the acrylonitrile units is no more than about 50% ofthe total weight or" the monomer units dispersed in unhardened gelatinhaving a jelly strength of approximately 50 grams Shoom.

References Qited in the file of this patent UNITED STATES PATENTS2,500,052 Yackel Mar. 7, 1950 2,834,676 Stanley et a1. May 13, 19582,848,434 Hallmann Aug. 19, 1958 2,893,867 Dawson et a1. July 7, 1959

1. A PHOTOGRAPHIC ELEMENT FROM WHICH PHOTOGRAPHIC PRINTS RESISTANT TOTROPICAL CONDITIONS MAY BE PREPARED WHICH COMPRISES A SUPORT BEARING ALAYER COMPRISING PHOTOSENSITIVE SILVER HALIDE AND A VEHICLE THEREFORCOMPOSED OF ABOUT 60-95% BY WEIGHT OF A WATER-INSOLUBLE RESIN SELECTEDFROM THE GROUP CONSISTING OF THE HOMOPOLYMERS OF ALKYL ACRYLATES, THEALKYL BEING 1-4 CARBON ATOMS AND THEIR COPOLYMERS WITH ACRYLONITRILE INWHICH THE LEVEL OF THE ACRYLONITRILE UNITS IS NO MORE THAN ABOUT 50% OFTHE TOTAL WEIGHT OF THE MONOMER UNITS DISPERSED IN UNHARDENED, LOW JELLYSTRENGTH GELATIN OF LESS THAN 100 GRAMS SHOOM JELLY STRENGTH.